Field of the Invention
The present invention relates to an acicular body, and more specifically, an acicular body which is formed containing chitosan.
Discussion of the Background
A percutaneous absorption method, which is a method for penetrating a substance such as drug to be delivered into the body through the skin so that the substance to be delivered is administered into the body, is used as a convenient way of painless administration of the substance to be delivered.
In the field of percutaneous administration using a percutaneous absorption method, a technique has been proposed in which an acicular body having a needle which is sized in the order of micrometers is used to pierce the skin, thereby administering a substance to be delivered such as drug into the skin (see PTL 1).
A method for manufacturing the acicular body has been proposed, in which an original plate is manufactured by machine processing, the original plate is used to fabricate a transfer plate, and the transfer plate is used for transfer molding (see PTL 2).
Another method for manufacturing the acicular body has been proposed, in which an original plate is manufactured by etching, the original plate is used to fabricate a transfer plate, and the transfer plate is used for transfer molding (see PTL 3).
The acicular body is preferably made of a material that is harmless to the body even if a broken piece of the acicular body remains in the body. Accordingly, biocompatible materials such as chitin and chitosan are proposed as materials for the acicular body (see PTL 4).
Chitin is a component contained in the shell of crabs and shrimps, and chitosan is a deacetylated chitin. Although chitin and chitosan are not explicitly divided, at least 70% deacetylated chitin is defined as chitosan.
Chitosan has a property of being insoluble in water but soluble in acidic aqueous solution. Accordingly, an acicular body made of chitosan can be manufactured by allowing water to be evaporated from the aqueous solution.
PTL 1: JP-A-S48-93192
PTL 2: WO 2008/013282
PTL 3: WO 2008/004597
PTL 4: WO 2008/020632